Sorry I hadn't checked this in a while. I *finally* got it all back together. It wasn't so difficult it's just that I kept changing my mind about things. Anyhow...

Gauging:

I think you'll find that 0-160 and 0-200 psi are common gages. I went with 160 to get more resolution, going to 200 would keep you closer to the middle of the range which in theory is more accurate. Since we aren't measuring anything too precise, cost may be the determining factor. Not that anyone asked but just an opinion.

When you say PVC pipe... I am thinking large white drain pipe for a house. I wouldn't use anything rigid. If you are thinking "tubing", PVC is OK with water but keep a few things in mind: 1) Flexibility, can it bend where you want without kinking? 2) Pressure - 9 bars is 135psi, and even though there will be some fudge factor built into any ratings on a tube you buy I'd still look for something that can handle a higher pressure than that, and 3) What I learned is that temperature rating matters as well. Even though a line to a gauge won't flow hot water, if it's near enough to the boiler (ie connected to the inlet, even if it's through a new OPV), it will get hot and may get soft! I used a "high pressure buna-N tubing" from McMaster-Carr. Reasonably flexible, rated for 250psi, Ok for use with water, and handles 220 degrees F.

As far as attaching it, simply put you will want to T it off of an existing line between the pump and the boiler, and in my opinion the closer to the coffee the better. For me it was convenient to put the T on the OPV. You could do it near the pump but I think that would be less accurate (however if you don't run a copper pipe like I did, the pump and boiler are close enough it should not matter where in that line you put it). But that's where a T needs to go, somewhere between the pump and the boiler inlet.

Something I did was to put the gauge low in the machine, so that any air in that line would bubble up and out. It felt more correct to not have air in it, however it may not actually matter, i don't know for sure. It also was easier for me to run the tubing keeping it low in the machine, it can very quickly get tough to put the top cover back on if you start cramming extra parts up there. If you have the 'twin' though you may not have room in that lower section, where my model did have a lot of empty space down there.

It probably would have been a better choice to have the OPV near the pump, but I haven't seen anything available that would go there. In short what I did was imitate what the Gaggia Classic owners seem to do, just adapted it to work with the Baby. I'm open to ideas on a different OPV location. You mentioned what's on the pump - FYI for the Baby's it's not adjustable, it's set for 11 bars. It would have to be replaced, the question is - with what? (I guess it is adjustable if you were to cut coils off the spring but it's not intended to be adjustable. I'd rather see a better solution, if you cut too much you're done. And with it all being plastic there I didn't want to disassemble and reassemble it too many times. And it being an irreversible mod as well...).

From what I've read when the Classic owners run things the way I have, they measure much more stabilized temperatures. I see what you mean, I'm sure it's not as good as it could be but apparently better than prior to the mod. I bought a 10' roll of copper tubing and had about 3' left, so... 7' of hot tubing is wrapped around the boiler. While a lot of the hot water is bled off, with the length, conductivity of the copper, short (25-ish seconds) duration, etc. hopefully it was worthwhile.

I've got "final" pictures on my cell phone, took them yesterday. I'll get them uploaded to my site and linked here ASAP.

I see an item #36 that looks about right. Looking up the part # on Google I see it mentioned but it doesn't look very easy (if possible) to purchase. Sure would have been nice - if that had been on my machine to start with it would have saved me some work!

Hard to tell with that parts layout drawing ... but, yeah, it looks about right (and the parts diagram looks to be the exact machine)

I've had a Carreza and a Coffee -- both of those had a really skinny OPV on the pump that didn't really do much and had a slotted adjustment (flat screwdriver). But the one I'm talking about is fat (like the drawing in your link) and has a larger adjuster that takes an allen wrench.

If you use that OPV, it sits down in a little well that leads back to the reservoir - does your machine have that?

Yes, the current OPV is basically a T - One part screws into the output of the pump, one is sent off to the boiler, and the 3rd returns to the pump inlet. It's down this 3rd one that the spring and everything are placed. Actually the same is true for the new OPV as well. You have to remove the return line to adjust it, then put it back. Quite a different OPV than OE but the plumbing description is the same.

I've got some more pictures up, final shots before I put it back together.

^ This is a shot of the inside, from underneath. You can see the original OPV pressure blow-off plugged up, and my new braided black hose that leads up to the copper pipe going around the boiler. Also in that area the new return tube from the new OPV. Guess you can also see that I labeled the wires so I knew where to put them back.

^ Upper section going back together. You can see the copper wrapped around the boiler, coming up from the pump underneath and ending up at the T on the side of the new OPV. That black tube off the T on the left connects to the gauge. You can see the OPV plumbed back to the pump, and the 3-way solenoid not yet hooked back up to its drain pipe. Lot of wiring still off.

^ Completed, sitting on the work bench in the basement waiting to be used.

I dialed in the OPV pressure a few nights ago, I epoxied over a filter basket I didn't use and I guess you'd say I turned it into a "blind" basket like you'd use for backflushing. I turned the steam wand valve open just enough to flow 2 oz. of water over 25 seconds, and fiddled with the OPV until that happened with the gauge also reading 9 bar the whole time (~ 135 psi). Did this with the heaters unplugged so I could flow water, not steam.

Been messing with the grinder lately, to get the coffee in the basket to hit my 2 oz / 25 sec combination, and finally did it this morning. These are pretty standardized #'s, so I have a starting point to tweak from now. Given enough time I'll play with the grind, pressure, etc. and see what changes.

I realized a few things - 1) After all this, the coffee seems to taste about the same, LOL. 2) I will likely soon open it up again and put in a PID so I can play with temperatures too. 3) I feel like I know these Gaggias well enough I just might start looking for "dead" ones on ebay and decide if it's worth buying, fixing and reselling them!

That is just gorgeous! I love that pressure gauge addition. It's a beauty.

It probably won't work on the Baby Twin, though, since the Baby Twin has a whole heap o' stuff already lodged in the pedestal where that tube comes down to the back side of the gauge. If it can be done at all, space constraints are going to be a major issue, probably.

Also, I just realized that the inside boiler area of the Baby Twin is quite different. There is a large circuit board, with multiple connections, close to the left side of the boiler (when viewed from the front). It is mounted on a sturdy piece of white plastic. The same material creates that "cage" around the boiler (presumably to keep things like wires away from the hot surface). Anyway, it makes the inside boiler compartment quite cramped already in the Baby Twin.

I'll post some images next time I open 'er up!

I have some images of the Baby Twin already, that might make some sense of what I'm describing, starting from the seventh post (I think) in this thread:

Thought I'd mention that I had previously swapped the black panarello tip with the chrome one (1 small hole to suck in air vs. 4). It made the frothing a lot better, the bubbles were much smaller, but they were still too much and the foam would cover the espresso in a sheet of white. Less thick than with the black one, but still too much to experiment with any "art".

I got to where I would keep a small piece of tape handy, and leave the hole uncovered for the first 15 - 20 seconds then cover it with tape for the rest of the duration. That worked much better but still seemed silly.

I recently installed the Silvia wand, and have only used it once (this morning). I didn't get enough foam on account of having to re-learn my technique again, but given other's reports I'm sure I'll get there. I can see already it's much easier to clean, just needing to be wiped off instead of pulled apart each time.

My real reason for updating is to say that with the Baby Class and the Silvia wand bought here: http://www.espressoparts.com/R_1054?&search_id=1611434 , the whole changeover process took about 5 minutes. Previously, Jon (Jkoll42) posted links to great pdf's describing a change-over and the work required. I'm happy to say that something with my machine or wand was different because I had no work to do whatsoever. The diameter and length of the tip of the new wand were identical to what came on the Gaggia originally. Even measured with a micrometer I got #'s within a thousandth or so. It was plug & play.

So - an easy mod for current or future Baby owners - the wand linked went right on. I can't say if it's better yet, need more time to play with it. But it couldn't have been easier to install.

That's very interesting - maybe they changed the specs of the stock wand. If you have a chance, could you give me a measurement of the diameter? I would like to update the PDF if there has been a change for the new machines. Lucky you! Check out the steam tutorials - I am a big fan of buying a gallon of milk for a new machine and just steaming and dumping until you get it right. With all the money we spend on equipment, $4 for a gallon is nothing to get it right!

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